It is well known that internal combustion engines have operating modes during which a high level of pollutants and unburned fuel are emitted. Such conditions may arise during idle, deceleration and acceleration modes of the engines.
Techniques have been proposed to improve an engine's fuel utilization and reduce the exhaust of pollutants by controlling the intake manifold pressure by supplying additional air to the intake manifold during idling, or deceleration of the engine.
Examples of such prior art techniques can be found in U.S. Pat. No. 3,659,575 to Lekka for use during engine idling or U.S. Pat. No. 3,977,372 to Fernandez during engine deceleration. Other patents describing devices for regulating intake manifold pressure to control fuel burning and exhaust of pollutants are U.S. Pat. No. 3,590,793 to Masaki; U.S. Pat. No. 3,575,386 to Boyd; U.S. Pat. No. 2,749,895 to Flint; U.S. Pat. No. 3,677,237 to Hansen; and U.S. Pat. No. 3,809,035 to Winton. Of particular interest are the U.S. Pat. No. 3,799,132 to MacGuire and U.S. Pat. No. 3,585,976 to Rider.
These prior art devices provide intake manifold pressure regulation during specific operating modes, but do not combine different fuel saving techniques applicable to different engine operating modes in a single structure.